Aims. The aim of this paper is to provide fundamental parameters and abundances with a high accuracy for a large sample of cool main sequence stars. This study is part of wider project, in which the metallicity distribution of the local thin disc is investigated from a complete sample of G and K dwarfs within 25 pc. Methods. The stars were observed at high resolution and a high signal-to-noise ratio with the ELODIE echelle spectrograph. The V sin i were obtained with a calibration of the cross-correlation function. Effective temperatures were estimated by the line depth ratio method. Surface gravities (log g) were determined by two methods: parallaxes and ionization balance of iron. The Mg and Na abundances were derived using a non-LTE approximation. Abundances of other elements were obtained by measuring equivalent widths. Results. Rotational velocities, atmospheric parameters (T eff , log g, [Fe/H], V t ), and Li, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, and Zn abundances are provided for 131 stars. Among them, more than 30 stars are active stars with a fraction of BY Dra and RS CVn type stars for which spectral peculiarities were investigated. We find the mean abundances of the majority of elements in active and nonactive stars to be similar, except for Li, and possibly for Zn and Co. The lithium is reliably detected in 54% of active stars but only in 20% of nonactive stars. No correlation is found between Li abundances and rotational velocities. A possible anticorrelation of log A(Li) with the index of chromospheric activity GrandS is observed. Conclusions. Active and nonactive cool dwarfs show similar dependencies of most elemental ratios vs. [Fe/H]. This allows us to use such abundance ratios to study the chemical and dynamical evolution of the Galaxy. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars.
We present the results of our analysis of spectroscopic observations of α UMi (Polaris) obtained in 1994 (five spectra) and 2001-2004 (30 spectra). The mean atmospheric parameters we derived are as follows:km s −1 in 2001-2004. A comparison of our T eff with those obtained from (B − V ) 0 data during the last 60 yr shows both sporadic and regular changes with a period of 25-30 yr, which is close to the orbital period, 29.9-30.5 yr. We also determined the colour excess E(B − V ) = 0.034 mag, A V = 0.102 mag, and chemical composition for 30 elements to verify the hypothesis that the star crosses the Cepheid instability strip for the first time. With [Fe/H] = +0.07 dex, Polaris shows [C/H] = −0.17 dex, [N/H] = +0.42 dex and [O/H] = −0.00 dex, which corresponds to the third (or fifth) crossing. On the basis of the distance, radius and surface gravity values, Polaris is probably a first-overtone pulsator. Polaris is located near the blue edges of the Cepheid instability strip for the fundamental mode and the first overtone, and an abrupt decrease of the pulsational amplitude and its recent increase could be due to its binarity.
We present results of a spectroscopic investigation of the A and B components of the visual binary VW Ari. Results are as follows: (1) The atmospheric parameters for the stars are T eff =7100 K, log g = 3.7 (A component), T eff =7300 K, log g =4.3, V f =1.9 kms" 1 (B component); ( 2) the masses and radii are: R a ^3.5Rq, R b «=T.6R q ; M A ^2.2M Q , M b «*1.8M 0 ; (3) abundances of 16 elements have been determined for VW Ari B. This star shows solarlike chemical composition for most of the elements. ( 4) Because of the complicated spectrum of VW Ari A (only a few very shallow lines are seen), we were able to estimate only Ca and Fe abundances in its atmosphere: [Ca/H]=-0.73, [Fe/H]=-0.46. The remarkable metallicity difference between the components strongly supports the hypothesis of stellar capture as the most probable origin of the VW Ari system.
Observations of the yellow hypergiant ρ Cas obtained in 2007-2011 in a wide wavelength region with spectral resolution R ≥60 000 have enabled studies of features of its optical spectrum in detail and brought to light previously unknown characteristics of the extended atmosphere of the star. The radial velocity measured from symmetric absorptions of metals varies with an amplitude of about ±7 km/s around the systemic velocity Vsys = −47 km/s, due to low-amplitude pulsations of the atmospheric layers near the photosphere. At some times, a velocity gradient was found in deep atmospheric layers of the star. A slight velocity stratification in the stellar atmosphere was detected for the first time, manifested as a difference of 3-4 km/s in the velocities measured from absorption lines of neutral metals and of ions. The long-wavelength components of split absorptions of BaII, SrII, TiII, and other strong lines with low excitation potentials for their lower levels are distorted by nearby emission lines. It is suggested that the short-wavelength components, whose locations correspond to the narrow velocity range Vr(blue) from approximately −60 to −70 km/s, are formed in a circumstellar envelope; one component of the D NaI doublet and the emission components of the FeII 6369.46 and 6432.68Å ions are also formed there.
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